The invention pertains to a flexible hose line, in particular, a high-pressure hose line which is subjected to a pressurized forming process, preferably for variable levels of pressure, and a process for manufacturing such hose lines according to the preamble of claims 1 and 12.
A flexible hose line for high-pressure media is known from DE 197 28 383 A1. This flexible hose line comprises an annular or screw-thread shaped corrugated metal hose, it is connected to a tubular connecting element, and it has a protective sleeve made of elastic, pliable material surrounding the outer sides of the hose line and the connecting element. In the region of the terminal corrugations adjacent to the connecting element, the protective sleeve features depressions that are directed radially inwards and that engage the valleys of the corrugations of the metal hose.
With such a solution, the transition region between the metal hose and the connecting element can be designed to accept a load.
The problem of the invention is to develop a hose line that can be exposed to high pressures and, in particular, that can withstand variable levels of pressure over a comparatively long period.
This problem is solved according to the invention by an inner layer that features a profile piece that can be elastically stressed at least in the longitudinal direction of the hose and that is the only layer that can be changed in length, by a reinforcing layer that is designed to absorb tensile forces acting in the longitudinal direction of the hose, by a compensation zone that is arranged between the inner layer and the reinforcing layer and that is used to compensate for relative movement between these layers and to support the inner layer in the radial direction on the reinforcing layer, and by connecting areas between the inner layer and the reinforcing layer, which are used to define the variable length of the inner layer as a predetermined useful length determined by the length of the reinforcing layer between the connecting areas.
The invention is associated with the advantage that a hose line with a large degree of flexibility can be exposed to high levels of pressure, in particular, to variable levels of pressure of large amplitudes. Such a possibility results from the large flexibility of the inner layer which is made less pressure-dependent by the reinforcing layer in connection with the compensation zone.
The application of pressure leads to shape and position changes of the inner layer that are limited by the reinforcing layer. This produces both a force acting against the axial expansion of the inner layer and also simultaneously a reaction force directed radially inwards and transmitted by the compensation zone. In this way, the compensation zone is used for the largely uniform reception and distribution of forces originating from the inner layer.
In a preferred embodiment of the invention, the profile piece of the inner layer is designed to be similar to a corrugated tube. The inner layer can also be a corrugated tube that can change in length for only small material stresses.
In another embodiment of the invention, the inner layer is formed by an element that can be pretensioned elastically in the axial direction and that is a component of the hose line in the pretensioned state. The pretensioning is advantageously chosen such that a certain pretensioning remains even for the largest possible pressure amplitudes in order to keep material fatigue low even for long use and high pulse-switching rates.
For special applications, e.g., the use of the hose line for media with an effect on the environment, the inner layer can be designed to have a high degree of gas impermeability, which is preferably achieved by making the inner layer out of a metallic material.
According to another embodiment of the invention, the reinforcing layer is formed from a mesh, in which the threads of the mesh feature an axial orientation and the preferred mesh angle xcex1, relative to the hose longitudinal axis, does not exceed 50xc2x0 and is advantageously within the range of 35xc2x0 to 45xc2x0.
In order to distribute the forces originating from the inner layer uniformly into the support body formed by the inner layer, the compensation zone, the reinforcing layer, and the connecting areas, the compensation zone is preferably formed from an elastomer, a thermoplastic elastomer, or a thermoplastic. Another favorable distribution of the forces introduced into the entire system is achieved by sinking the compensation zone into the profile piece of the inner layer or filling up the profile piece with the compensation zone at least in the connecting areas.
A method according to the invention for manufacturing a flexible hose line is realized in that the inner layer and/or the reinforcing layer are provided with a compensation zone bonded to each layer, in that the inner layer and the reinforcing layer are brought into the required position relative to each other through relative movement, and in that the inner layers are connected to the reinforcing layer in the region of the hose line fittings.
In an advantageous execution of the method, the inner layer is pretensioned in the longitudinal direction of the hose line before the inner layer and the reinforcing layer are connected in the region of the hose fittings.
A force-fit and/or positive-fit connection between the inner layer and the reinforcing layer can be produced advantageously through radial forces on the component surrounding the reinforcing layer.